1. Field of the Invention
The present invention relates to a substrate treatment method and a substrate treatment apparatus for treating a substrate with a treatment liquid. Examples of the substrate to be treated include semiconductor wafers, glass substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, substrates for photo masks, ceramic substrates, and substrates for solar cells.
2. Description of Related Art
In production processes for semiconductor devices and liquid crystal display devices, substrate treatment apparatuses of a single substrate treatment type are often used, which are adapted to perform a treatment on a single substrate (e.g., a semiconductor wafer or a liquid crystal display glass substrate) at a time for treating a front surface of the substrate with a chemical liquid.
The substrate treatment apparatus of the single substrate treatment type includes a spin chuck which horizontally holds and rotates the substrate, a chemical liquid nozzle which supplies the chemical liquid to the front surface of the substrate rotated by the spin chuck, and a deionized water nozzle which supplies deionized water to a center portion of the front surface of the substrate rotated by the spin chuck.
In the substrate treatment apparatus of the single substrate treatment type, the chemical liquid is supplied from the chemical liquid nozzle onto the front surface of the rotated substrate. Thus, the front surface of the substrate is treated with the chemical liquid (chemical liquid treatment step). After the supply of the chemical liquid is stopped, the deionized water is supplied from the deionized water nozzle onto the center portion of the front surface of the substrate. The deionized water supplied onto the front surface of the substrate receives a centrifugal force generated by the rotation of the substrate to flow toward a peripheral edge of the substrate over the front surface of the substrate. Thus, the chemical liquid is rinsed away from the substrate with the deionized water (rinsing step). In the rinsing step, the substrate is rotated at the same rotation speed as in the chemical liquid treatment step. The flow rate of the deionized water supplied from the deionized water nozzle is constant, and generally equals to a chemical liquid supply flow rate. After the supply of the deionized water is stopped, the rotation of the substrate is accelerated, and the deionized water is spun away from the substrate. Thus, the substrate is dried, and a series of treatment steps are completed.
Two exemplary methods for supplying the chemical liquid to the substrate include a center spouting method, and a scanning method. In the center spouting method, the chemical liquid is spouted toward the rotation center of the front surface of the substrate rotated by the spin chuck (JP-A-2005-286221). In the scanning method, the chemical liquid nozzle is moved above the substrate (see JP-A-2007-88381). More specifically, the chemical liquid is supplied from the chemical liquid nozzle onto the front surface of the substrate rotated by the spin shuck, while the chemical liquid nozzle is moved over the substrate.
In the substrate treatment apparatus of the single substrate treatment type, a chemical liquid heated up to a higher temperature may be used to increase the treatment speed. The chemical liquid supplied from the chemical liquid nozzle has a higher temperature immediately after being supplied onto the front surface of the substrate, but is deprived of heat by the substrate and the ambient environment when flowing over the front surface of the substrate. Thus, the temperature of the chemical liquid is reduced. Therefore, the higher temperature chemical liquid supplied onto the front surface of the substrate from the chemical liquid nozzle has the highest treatment ability at a chemical liquid supply position.
During the supply of the chemical liquid by the center spouting method, the chemical liquid supplied onto the center portion of the front surface of the substrate receives a centrifugal force generated by the rotation of the substrate to flow toward the peripheral edge on the front surface of the substrate to spread over the entire front surface of the substrate. Where the chemical liquid heated up to a higher temperature is used, the chemical liquid has a relatively high temperature on the center portion of the substrate, and has a relatively low temperature on the other portion of the substrate. This results in variations in treatment efficiency within the front surface of the substrate. That is, the chemical liquid treatment proceeds at a higher treatment rate on the center portion of the front surface of the substrate, and proceeds at a lower treatment rate on the other portion of the front surface of the substrate. As a result, the front surface of the substrate is unevenly treated.
During the supply of the chemical liquid by the scanning method, on the other hand, the chemical liquid supply position is moved over the front surface of the substrate by the movement of the nozzle. That is, the chemical liquid supply position is moved (scanned) between the rotation center and the peripheral edge of the front surface of the substrate.
However, the scanning method also fails to evenly perform the chemical liquid treatment on the front surface of the substrate by supplying the chemical liquid heated up to a higher temperature onto the substrate. That is, a movement speed at a point on the front surface of the substrate is increased, as a distance between the point and the rotation center of the substrate increases. Therefore, if the chemical liquid supply rate is constant, the amount of the chemical liquid supplied to a unit area of the front surface of the substrate is reduced as a distance between the chemical liquid supply position and the rotation center increases. This results in variations in treatment efficiency within the front surface of the substrate. More specifically, the chemical liquid treatment proceeds at a relatively high rate on the center portion of the front surface of the substrate, and proceeds at a relatively low rate on the other portion of the front surface of the substrate. Even if the higher temperature chemical liquid is supplied onto the substrate by the scanning method, it is impossible to evenly perform the chemical liquid treatment on the front surface of the substrate.